Ischemia-induced changes in the immunoreactivity for endothelin and other vasoactive peptides in the brain of the Mongolian gerbil

Immunoreactivity for vasoactive peptides [endothelin (ET); calcitonin gene-related peptide (CGRP); atrial natriuretic peptide (ANP); neuropeptide Y (NPY)] was investigated in nervous tissue of Mongolian gerbils in which the common carotid artery (CCA) was temporarily occluded (30 min-4 h) on one side, provoking transient unilateral ischemia at the forebrain level. Observations were carried out in a group of animals that were perfused promptly after CCA reopening, and in a group of animals that were perfused 12 h later. In animals of the first group, darker immunostaining was usually observed for most peptides in the forebrain ipsilateral to the CCA occlusion. Computer-assisted densitometric analysis showed that the asymmetry was relevant for ET, CGRP, and ANP, and almost undetectable for NPY. In animals of the second group, areas of tissue degeneration were observed. In these areas, ET immunoreactivity was markedly denser, whereas immunoreactivity for the remaining peptides was about at the background level. It is concluded that ischemia induces an increase in both vasoconstrictor and vasodilator peptides that in areas of moderate ischemia might maintain a residual tissue perfusion. In areas of severe hypoxia, a predominant ET-induced vasoconstriction would contribute to tissue damage.